JP2002518644A - Flexible shaft coupling for drive unit shaft for infusion pump - Google Patents

Abstract

(57) [Summary] A drive connector for elastomerically connecting a drive shaft to a driven shaft. The elastomeric coupling 42 includes openings 74, 80 at opposite ends, which are generally "D" shaped and have correspondingly shaped ends of the drive and driven shafts. An interference fit is formed between them. A web 98 extends transversely within the interior of the elastomeric coupling so as to limit the distance at which the drive and driven shafts are inserted inside the opening of the coupling. ing. The shaft coupling includes a rib 72 extending longitudinally along the outer surface length. The sleeve 86 is provided with a groove 90 corresponding in size and shape to the rib, which sleeve is slip-fitted to its coupling and connected to the driven shaft.

Description

DETAILED DESCRIPTION OF THE INVENTION

TECHNICAL FIELD The present invention relates generally to a connector for use in connecting a motor drive shaft to a driven shaft, and more particularly, to a pharmaceutical infusion pump, wherein the motor drive shaft is a plunger in the pump. Connected to a camshaft that drives
The present invention relates to an elastomer coupler for providing a restoring force to a plunger.

BACKGROUND OF THE INVENTION In many devices driven by portable motors, a small direct current (DC) motor is rotatably connected to a driven shaft using a rigid metal coupler. Such a coupling has a short section of thick tubing having two threaded holes in the tubing wall adjacent each end. A set screw is screwed into each hole. These set screws secure the driven shaft inserted into the other end of the coupler to engage the drive shaft of the motor inserted into one end of the coupler. It is tightly tightened.
Even if the fastener locking material is applied, these set screws often become loose with use, causing shaft damage and failure of the devices incorporating these couplers.

[0003] Couplings are generally available from component manufacturers only to a limited extent. If the coupler used to connect the two axes is too large, the coupler will not connect the axes properly and the mass will be distributed symmetrically about the centerline of the two axes. Otherwise, vibration may be caused. In addition, conventional couplers generally require that the centerlines of the two connected axes be relatively accurately centered. Thus, for example, misalignment between the motor drive shaft and the driven shaft, even if slight, can cause side loading of one or both shafts, creating greater bearing wear.
The rigid coupling transfers noise and vibration from the motor to other parts of the device in use.

[0004] Ideally, a more flexible shaft coupling is preferably provided between the motor drive shaft and the driven shaft. Large motor couplings sometimes include a fiber reinforced rubber assembly that is clamped around the ends in two axes to provide some flexibility, but such couplings have been used in smaller devices. Too large to use.

[0005] It is therefore clear that it would be preferable to use a simple coupling, which addresses the problems mentioned above and has a relatively low cost, in a device driven by a small electric motor. The prior art does not provide a suitable alternative to the prior art rigid metal connectors of the type described, or to the oversized and cumbersome prior art fiber reinforced rubber connector assemblies.

SUMMARY OF THE INVENTION According to the present invention, there is provided a coupler for connecting a non-cylindrical end of a drive shaft to a non-cylindrical end of a driven shaft. The coupler includes a generally cylindrical fitting with opposing first and second ends. A first opening is provided at a first end of the fixture, and a second opening is provided at a second end of the fixture. The first opening has a size and shape substantially corresponding to the size and shape of the non-cylindrical end of the drive shaft. Similarly, the second opening has a size and shape substantially corresponding to the size and shape of the non-cylindrical end of the driven shaft. The fitting is adapted to resiliently expand when the first opening is pressed over the drive shaft and the second opening is pressed over the driven shaft, resulting in an interference fit in each case. It is formed from an elastomeric material. The fixture is adapted to thereby drive connect the drive shaft to the driven shaft.

[0007] Preferably, the fixture further comprises a web disposed between the first opening and the second opening transversely to the longitudinal axis of the fixture. The web limits the depth at which the drive and driven shafts penetrate into the first and second openings, respectively. Also, the vibration of the drive shaft transmitted from the drive shaft to the driven shaft is limited by the web.

[0008] A sleeve sized to fit snugly around the outer surface of the fitting provides a compressive force that facilitates fitting of the fitting onto the drive shaft. The outer surface of the sleeve includes a cam surface adapted to act on the plunger. As the drive shaft rotates the driven shaft, the sleeve causes the plunger to move along the longitudinal axis of the plunger. Preferably, the cam surface is adapted to apply only one-directional force on the plunger, and the plunger is preferably biased in the opposite direction by an elastomeric membrane displaced by the plunger.

The outer surface of the fitting is keyed to the inner surface of the sleeve. Also, the inner surface of the first opening includes a flat portion that is adapted to seat a corresponding flat portion formed at the end of the drive shaft. Similarly, the inner surface of the second opening includes a flat portion adapted to seat a corresponding flat portion formed at the end of the driven shaft.

Thus, the elastomeric fitting minimizes the transmission of vibration between the drive shaft and the driven shaft, and the fitting also helps to minimize audible noise. According to this attachment, due to its elasticity, misalignment between the drive shaft and the driven shaft can be allowed to at least a limited extent.

The above-described aspects and attendant advantages of the present invention will become more readily appreciated as the invention becomes more fully understood by reference to the following detailed description, taken in conjunction with the accompanying drawings, in which: There will be.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, an exemplary application of the present invention is shown for use in pumping a pharmaceutical fluid through a pump cassette 10. The pump cassette 10 is disposable and is intended for use on a single patient. Details of this pump cassette are disclosed in commonly assigned U.S. Pat. No. 5,586,867, the drawings and specification of which are specifically incorporated by reference. Proximal tubing 14 and distal tubing 16 are connected to the proximal and distal ends of the pump cassette. Pharmaceutical fluid container (not shown)
Is connected to the proximal tubing 14 and the distal tubing 16 is connected to the patient's cardiovascular system so that the medicament fluid is infused at a rate determined by the speed at which the pump cassette 10 is driven. ing. The pump cassette 10 includes a plastic housing 12, which has an opening 18 formed in an upper surface thereof. From the opening 18, an elastomeric film 20
Is exposed and the membrane is sealed between the top and bottom portions of the plastic housing. The lower surface of the elastomer film 20 is exposed to the flow path via the pump cassette 10 and the elastomer film 20 is
Acts to transfer the pharmaceutical fluid when pushed inward into the interior of the device. The pump cassette is latched into the pump chassis 22 shown in FIG. The pump chassis is mounted in a pump housing (not shown) including a battery power supply, electronic components for controlling the pumping operation, and a user interface, all of which are not shown. The pivot member 25 of the pump chassis 22 includes:
It is spring biased and engages the housing 12 of the pump cassette 10 to latch the pump cassette 10 in place inside the pump chassis. The details of this latching mechanism and other aspects of the pump chassis are not relevant to the present invention and are not disclosed herein.

The drive assembly 24 provides a force to deflect the elastomeric membrane 20 into the interior of the pump cassette 10 and to pump pharmaceutical fluid into the patient. Another detail of the drive assembly and its interaction with the pump cassette is shown in FIGS. 3, 4 and 5. The drive assembly 24 includes a dc motor 28 energized by current provided through a flexible lead 30 which includes a printed circuit board (shown in FIG. 1) inside the pump. None) is a connector plug 32 adapted to couple to a mating connector. A resilient O-ring support 34 is provided around the outer surface of the motor 28 and is housed within a pair of drive shrouds 26a and 26b. These shrouds are secured around the drive assembly and generally surround and hold the assembly, as shown in FIG. Second
A resilient O-ring support 36 is located at the end of the DC motor 28 to provide additional support of the motor and drive assembly within the drive shrouds 26a and 26b. Immediately ahead of the O-ring 36, a drive shaft 38 extends from the end of the DC motor 28 and is connected to a shaft joint 42 made of an elastomer material. The shaft coupling 42 is also connected to the driven shaft 40, and transmits rotational force to the drive shaft 3.
8 to the driven shaft 40.

The details of the interior of the shaft coupling 42 are illustrated in FIG. As shown in FIG. 2 and FIGS. 1 and 4, a part of the drive shaft 38 connected to the shaft coupling 42 includes:
A flat portion 76 is provided on one side so that the shape is substantially "D" shaped. This part of the drive shaft 38 extends into an opening 74 in the coupling 42. The opening 74 also has a flat portion 78 at a part of its periphery, so that the shape of the opening is also “D” -shaped, but the size of the opening is larger than that of the end of the drive shaft 38. Slightly smaller. In this manner, the shaft coupling 42 has the end of the drive shaft connected to the opening 74 of the shaft coupling.
Forms an interference fit with the drive shaft 38 when inserted therein. Shaft coupling 42
At the opposite end, an opening 80 is located remote from the opening 74, and the opening 80 is provided with a flat 82 on one side and therefore has a substantially "D" cross-sectional shape. . A flat portion 84 is formed at the end of the drive shaft 40 so that the shape of this opening is also "D" shaped, but the drive shaft 40 is slightly larger in size than the opening 80. In this way, an interference fit is also formed when the driven shaft 40 is inserted into the opening 80 of the shaft coupling 42. A transverse web 98 (shown in FIG. 2) is disposed inside the coupling 42 to separate the opening 74 from the opening 80 and limit the extent to which the drive shaft 38 and the driven shaft 40 extend within the coupling 42. are doing. The transverse web 98 prevents the end of the drive shaft and the end of the driven shaft from contacting each other,
Transmission of vibration from the drive shaft 38 to the driven shaft 40 is limited.

The outer surface of the shaft coupling 42 is substantially cylindrical, but on one side, a rib 72 extends substantially parallel to the longitudinal axis of the shaft coupling. The rib 72 has a semicircular cross section. The shaft coupling is
Since it is made of an elastomeric material, preferably synthetic rubber, either or both the drive shaft 38 and the driven shaft 40 can rotate within the joint when the joint is distorted. A sleeve 86 is provided to prevent such distortion and the resulting slippage. The sleeve extends neatly over the entire outer surface of the coupling 42, with one of said shafts distorting the coupling sufficiently to form a "D" shaped opening formed at the end of the coupling. A compression force is created that prevents it from trying to rotate inside. The sleeve 86 has an opening 88, the inside diameter of which is approximately equal to the outside diameter of the shaft coupling 42. Further, a cross-sectional profile and size corresponding to the cross-sectional profile and size of the rib 72 is provided, and a longitudinally extending notch 90 is formed on one side of the opening 88 to form a sleeve. The rib is adapted to be received when the 86 is slidingly fitted to the shaft coupling 42. The coupling 42 may be provided with alternative cuts to receive correspondingly shaped and sized ribs formed on the inner surface of the opening into the sleeve 86 to key the coupling and sleeve. It will be clear that it is good. In a preferred embodiment, sleeve 86 is a molded part that includes a rigid inner element (not shown) formed from a rigid plastic or metal material and coated or molded with an elastomeric material, preferably synthetic rubber. .

Immediately behind the flat portion 84 on the driven shaft 40, there is a circular groove 92 (FIG. 3) that engages the inner elastomeric portion of the sleeve 86 so that the sleeve is
It is fixed to the end of the driven shaft 40 connected to the shaft coupling 42. The sleeve 86
The interference with the entire flat portion 84 of the driven shaft 40 can prevent the driven shaft 40 from rotating. The use of the sleeve 86 thus facilitates the transmission of rotational force from the drive shaft 38 to the driven shaft 40.

Some significant advantages are obtained by using a coupling 42 to connect the drive shaft 38 and the driven shaft 40. Due to the elastomeric nature of the shaft coupling 42, the shaft coupling allows some misalignment between the centerline of the drive shaft 38 and the centerline of the driven shaft 40, so that the side surface on either the driven shaft or the drive shaft The load decreases. The reduction in side loads improves the operating life of the drive assembly, especially the life of bearings 46 and 50. In addition, the reduction in side loads increases the operating life of the motor, and the drive shaft of the motor does not require more expensive bearings than would be required to handle the higher side loads. The cost of using a motor can be reduced. In addition, the coupling 42 eliminates the need for mechanical fasteners to attach the drive shaft 38 to the driven shaft 40, and
Since the vibration of the motor is at least partially isolated from the components of the drive assembly downstream of the coupling 42, the noise level of the drive assembly is reduced. Compared to prior art devices for coupling a drive shaft to a driven shaft, the coupling 42 is relatively small and compact. Furthermore, since the assembly of the coupling and the sleeve is relatively simple, the reduction of the assembly time and the number of parts and the resulting cost reduction of the drive assembly are reduced by the prior art type coupling. Rather, it is achieved by using the shaft coupling 42 and the sleeve 86.

The sleeve 86 is useful for yet another purpose in this exemplary application of the invention. In particular, the sleeve 86 includes a cam surface 96 that defines a contour having a locus of varying radial distance from the centerline of the driven shaft 40. When the drive shaft 38 rotates the driven shaft 40 and the sleeve 86, the cam surface 96 rotates. The rotating cam surface exerts a force that is used to displace the plunger 58 and move the plunger 58 toward the pump cassette. Plunger foot 62 is formed at the end of plunger 58 and contacts elastomeric membrane 20 in pump cassette 10. The plunger 58 includes
Two O-rings 64 are included that seal the interior surface of the opening 66 in the pump chassis 22 (FIG. 6), thereby helping to prevent water or other liquids from entering the interior of the pump housing.

The cam surface 96 is formed only on a part of the outer surface of the sleeve 86. Cam surface 96
Are not radially equidistant from the center line of the driven shaft 40. The bearing 46 fits in this portion of the sleeve 86 and facilitates holding the drive assembly during rotation of the drive and driven shafts.

As shown in FIGS. 1, 3 and 5, drive assembly 24 also includes a bearing 50 around driven shaft 40. The bearing 50 is held in place by a clip 52 that fits inside an annular groove 94 formed in the driven shaft 40 (see FIG. 3). A clutch assembly 54 is disposed ahead of the clip 52 on the drive shaft 40. The clutch assembly 54 includes a roller clutch 68. An encoder tab 56 is disposed at an end of the driven shaft 40 remote from the sleeve 86. This encoder tab is used to determine the home position of the driven shaft 40 for the purpose of controlling the drive assembly and other purposes not related to the present invention.

A cam bearing 48 is disposed about the cam surface 96 and comprises a radial ball type bearing. This cam bearing acts as a friction reducing interface between the cam surface 96 and a loop 60 formed at the end of the plunger 56 opposite the end where the plunger foot 62 is located. . The loop 60 is generally shaped like a square with rounded corners. The cam surface 96 does not apply any force to move the plunger 56 away from the elastomeric membrane 20, so that the radially outer surface of the cam bearing 48 does not contact the upper inner portion 100 of the loop 60. Instead, the elastomeric membrane is
Is lifted upward to provide a restoring force that separates the pump cassette 10 from the inside. The cam bearing 48 contacts the other inner portion of the loop 60 and displaces the elastomeric membrane 20 to the inside of the pump cassette, thereby dispensing the medicinal liquid to the distal line 1.
6 to provide a force to drive plunger 56 toward pump cassette 10. The gap between the cam bearing 48 and the surface 100 of the loop 60 is slightly
3 mils, which means that any frictional movement between the outer surface of the cam bearing and the inner surface of the loop will reduce the efficiency with which the plunger 56 is driven by the drive assembly 24. That's enough to prevent it.

Although the present invention has been described with reference to preferred embodiments thereof, those skilled in the art will recognize many modifications that may be made within the scope of the appended claims. . Accordingly, the scope of the invention is not intended to be limited in any way by the above description, but instead is solely determined by reference to the appended claims.

[Brief description of the drawings]

FIG. 1 is an exploded isometric view of a motor and a drive assembly according to the present invention, illustrating a pump cassette in which medicinal fluid is pumped by a plunger actuated by the drive assembly.

FIG. 2 is an isometric view of an elastomer coupler for coupling a drive shaft to a driven shaft.

FIG. 3 is a cross-sectional side view of the drive assembly.

FIG. 4 is an exploded isometric view showing the motor and a portion of the drive assembly.

FIG. 5 is an isometric view of the motor, drive assembly, plunger and pump cassette.

FIG. 6 is an exploded isometric view of the motor, drive assembly, plunger and pump chassis.

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Lawless, Michael Daville, United States, Calif. Daymouth, Marshall Court 111 (72) Inventor Soveron, Peter A. United States, Calif.・ Alto, California, Avenille ・ 411 F term (reference) 3H071 AA01 CC33 CC34 DD45 EE07 4C066 BB01 CC01 DD02 DD11 HH01 HH30 JJ02 QQ93 [Continued abstract]

Claims (21)

[Claims] 1. A substantially cylindrical fixture having opposite first and second ends, wherein a first opening is disposed at a first end of the fixture, and wherein the first opening is disposed at a first end of the fixture. A second opening is provided at a second end, the first opening has a size and shape substantially corresponding to the size and shape of the non-cylindrical end of the drive shaft, and the second opening is Having a size and shape substantially corresponding to the size and shape of the non-cylindrical end of the driven shaft, wherein the fitting has a first opening pressed over the drive shaft in an interference fit; The aperture is formed from an elastomeric material adapted to spread when the opening is pressed over the driven shaft in an interference fit, whereby the fitting is adapted to drive connect the drive shaft to the driven shaft. The non-cylindrical end of the drive shaft, which is provided with a fixture, Hitch to connect. 2. The fixture further comprises a web disposed between the first opening and the second opening across a longitudinal axis of the fixture, the web having a drive shaft and a driven shaft. 2. The coupling of claim 1, wherein the coupling limits the depth of each of the first and second openings. 3. The web limits vibration of the drive shaft transmitted to the driven shaft.
The coupler according to item 1. 4. The compression further comprising a sleeve sized to fit in an interference fit around an outer surface of the fixture, thereby maintaining the drive shaft seated in the first opening. The coupler of claim 1, wherein a force is provided. 5. The sleeve of claim 4, wherein the outer surface of the sleeve comprises a cam surface adapted to act on the plunger, the cam surface driving and moving the plunger when the drive shaft rotates the driven shaft. The coupler according to item 1. 6. The coupling of claim 5, wherein the cam surface is adapted to apply only one-way force on the plunger, and wherein the plunger is biased in an opposite direction by an elastomeric membrane. 7. The coupler of claim 4, wherein the outer surface of the fitting is keyed to the inner surface of the sleeve. 8. The coupler of claim 1, wherein the inner surface of the first opening includes a flat portion adapted to seat a corresponding flat portion formed at an end of the drive shaft. 9. The coupling according to claim 1, wherein the inner surface of the second opening includes a flat portion adapted to seat a corresponding flat portion formed at an end of the driven shaft. 10. An elastic coupling assembly for transmitting rotational driving force from a first shaft to a second shaft, comprising: (a) a generally long elastomer member; and (i) one end of the elastomer member. And a first hole sized to provide an interference fit over the first shaft, and (ii) disposed at an opposite end of the elastomeric member and tightened over the second shaft. An elastomeric member having a second hole sized to provide a fit; and (b) a central opening sized to provide an interference fit over an outer surface of the elastomeric member; And a long sleeve for providing a compressive force that holds the elastomeric member at least in one of the first shaft and the second shaft relative to the elastomeric member, such that the shafts are connected to each other via the elastomeric member. When An elastic shaft coupling assembly comprising: 11. The elastic shaft coupling according to claim 10, wherein the elastomer member comprises a transversely extending web and is disposed between the first hole and the second hole. 12. At least a part of the first shaft inserted into the first hole,
The resilient shaft coupling of claim 10, including a flat area, and wherein the first hole includes a corresponding flat area that provides an interference fit with the first shaft. 13. At least a part of the second shaft inserted into the second hole,
The resilient shaft coupling of claim 10, including a flat area, and wherein the second hole includes a corresponding flat area that provides an interference fit with the second shaft. 14. The apparatus of claim 10 wherein at least one of the sleeve and the outer surface of the elastomeric member includes a centering groove for keying the position of the driven shaft.
An elastic shaft coupling according to item 1. 15. The sleeve and an outer surface of the elastomeric member include a centering ridge sized to fit within the centering groove, wherein the centering groove and the centering ridge are connected to each other. The resilient coupling of claim 14, wherein the resilient coupling cooperates to provide an interference fit between the elastomeric member and the sleeve. 16. The sleeve of claim 1, wherein the outer surface of the sleeve includes a cam surface having a profile defining a locus of locations at a radius that varies with respect to a central axis of the elastomeric member.
The elastic shaft coupling according to 0. 17. The resilient coupling of claim 16, further comprising a link having a substantially quadrilateral opening through which the sleeve extends, wherein the link rides over the cam surface of the sleeve as the sleeve rotates. 18. The resilient coupling of claim 17, wherein the link is coupled to a plunger that is driven to move away from the sleeve when the cam surface rides on one side of the quadrilateral opening. 19. The elastomeric member of claim 10, wherein the elastomeric member is adapted to accommodate a misalignment between the first shaft and the second shaft when the first shaft and the second shaft are connected to each other. Elastic shaft coupling. 20. The elastic coupling of claim 10, wherein the sleeve comprises an elastomeric material molded over a rigid material. 21. A shaft mounted on the chassis and adapted to be rotationally driven by the prime mover for rotating the cam surface; and (b) a first end coupled to the cam surface. And a second end opposite the second end.
A plunger mounted to reciprocate back and forth in the direction, wherein the first end of the plunger has a first end facing the pump cassette by a force applied to the plunger by the cam surface when the shaft rotates. (C) an elastomeric membrane exposed in an opening formed in the face of the pump cassette, said pump cassette being removably mounted in a chassis at a predetermined position; As a result, the opening is disposed near the second end of the plunger, said second end of the plunger displacing the elastomeric membrane inside the pump cassette, causing fluid to flow through the pump cassette, The elastomeric membrane provides a restoring force that biases the plunger and moves the plunger in a second direction toward the cam surface.
A drive mechanism for a pump cassette, wherein the cam surface has an elastomeric membrane that does not apply a force to move the plunger in the second direction.